Rear shocks.

[Julio A.]

I might be purchasing this Brand New rear shocks here:

http://www.ebay.com.au/itm/BMW-R45-R65-Classic-Shocks-/220850913627?pt=AU_Motorcycle_Parts_Accessories&hash=item336bbd815b#ht_940wt_932

It said that the distance between the centers are 325mm Which is roughly 12.8''.

But past posts state that the distance are supposed to be 13'' spot on.
Would the 0.2 difference in inches affect anything?  

[Barry]

I've seen both 12.8" and 13" referred to as the stock dimensions. Mine measure 12.8" Others have measured 13" Some of the after market suppliers say 12.8" and others say 13". I've never seen a definitive figure in print other than "mine measure 13" or "mine measure 12.8" I suppose it's even possible 78 -80 models are different to 81- on.

To be pedantic both figures are likely wrong as the original Boge units would have been metric but that's beside the point which is that in light of all the other differences 0.2" probably doesn't  matter. The only time the units will be at full extension is on the stand or on full rebound. The rest of the time the ride height will be determined by the spring rate and amount of pre-load. The reason people worry about shock length is they don't want to upset the suspension geometry or make the bike hard to put on the stand. That overlooks the fact that you could have 2 different makes of shock which were both 13" but had different ride height because the springs were not the same. Or you could have a 12.8" shock that rode higher and was easier to put on the stand than a 13" shock because the spring rates or pre-load was different. On top of that the aftermarket shocks all have different amounts of travel to the Boge units. Obviously shock lengths that are grossly incorrect would be no good but 0.2" difference could easily be swallowed up by other variables and so likely doesn't matter.

Getting the correct spring rate does matter which is why the best  suppliers are those who will build you a shock which is correct for your weight.

[montmil]

You will not likely notice any difference in handling. But, shorter shocks do add a degree of difficulty in pulling the R65 up, over and onto the center stand.

If your particular bike also has the hernia-inducing "ball end" center stand... well, that's another point off in the Olympic judging handbook.

I threw away a "short" pair of 325mm Progressive rear shocks that were on my '81 and went with longer Hagons and 100# springs as recommended by Dave Quinn, the Hagon go-to guy in the US.

Now I need to order another pair for the '83.